JPH0532257B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a four-wheel drive control device, and in particular, the present invention relates to a four-wheel drive control device, and in particular, to absorb the turning radius of the front and rear wheels that occurs during cornering. The present invention relates to a four-wheel drive control device for a four-wheel drive vehicle equipped with a center differential for allowing a difference in rotational speed.

[Conventional technology]

Generally, the left and right wheels of a vehicle have different turning radii when cornering. Therefore, in order to absorb this effect and perform smooth cornering, vehicles are generally equipped with a mechanism that allows the difference in rotation speed between the left and right wheels depending on the difference in turning radius, that is, a differential mechanism (front differential, rear differential). ing.

On the other hand, this phenomenon, that is, the difference in turning radius, also occurs between the front wheels and the rear wheels, so in a four-wheel drive vehicle, the difference in rotation speed between the front and rear wheels is allowed according to the difference in turning radius. A mechanism equipped with a center differential mechanism has been proposed.

[Problem that the invention seeks to solve]

However, since this center differential has the function of distributing torque between the front and rear wheels in an equal ratio, the driving force transmission limit will be balanced to the lower value of the driving force of the front or rear wheels. . In other words, the maximum traction force Fμ is calculated by assuming that the front wheel limit traction force is Fμ _f and the rear wheel limit traction force is Fμ _r.For simplicity, consider the case where the torque distribution ratio of the center differential is 1:1. 4-wheel drive vehicle: Fμ ₁ = 2×Fμ _r (if Fμ _f < Fμ _r ) 4-wheel drive vehicle without center differential or with a locked center differential: Fμ ₂ = Fμ _f + Fμ _r , and Fμ ₁ < Fμ It turns out that it is ₂ .

For this reason, a four-wheel drive vehicle with a center differential may have inferior transmitted driving force when the road surface friction coefficient is low, compared to a four-wheel drive vehicle without a center differential.
For example, when a large driving force is generated, such as during acceleration, this driving force cannot be sufficiently transmitted to the road surface, and this appears as phenomena such as slipping of the front or rear wheels. A four-wheel drive control system with a removable center differential has not yet been proposed.

The present invention solves the above-mentioned problems by reliably detecting the point in time when an adverse effect is caused by the center differential mechanism, and when this is detected, locking the center differential mechanism to ensure that the center differential function is fully functional. It is an object of the present invention to provide a four-wheel drive control device that allows the four-wheel drive to exhibit its full potential and does not cause a decrease in driving force.

[Means for solving problems]

To this end, the four-wheel drive control device of the present invention is equipped with a center differential that absorbs the difference in rotational speed between the front wheels and the rear wheels so as to absorb the difference in turning radius between the front wheels and the rear wheels that occurs during cornering. In a wheel drive control device, the accelerator opening degree and the rotational speed of the front and rear wheels are detected, and the rate of change in the rotational speed of the front and rear wheels is compared with the rate of change in the accelerator opening degree. The present invention is characterized by a mechanism that locks the center differential and disables the operating mechanism when the rate of change in the rotational speed of the center differential becomes significantly larger than the rate of change in the accelerator opening.

[Action and effect of invention]

The four-wheel drive control device of the present invention detects the accelerator opening and the rotation speed of the front and rear wheels, and compares the rate of change in the rotation speed of the front and rear wheels with the rate of change in the accelerator opening, The center differential is equipped with a mechanism that locks the center differential and disables the operating mechanism when the rate of change in the rotation speed of the front or rear wheels becomes significantly larger than the rate of change in the accelerator opening. In addition to operating the system to achieve smooth running conditions, in the event of an abnormal condition such as a slip, the system quickly detects such a condition and locks the center differential. The running condition can be maintained.

〔Example〕

Examples will be described below with reference to the drawings.

FIG. 1 shows one of the control systems in the control device of the present invention.
A diagram showing the configuration of an embodiment, FIG. 2 is a diagram for explaining the flow of processing by the control device of the present invention, and FIG. 3 is a power transmission system of a four-wheel drive vehicle with a center differential to which the control device of the present invention is applied. 4 is a diagram showing a time chart of various variables when no slip occurs, and FIG. 5 is a diagram showing a time chart of various variables when a slip occurs. In the figure, 1
is an accelerator opening detection unit, 2 is a front/rear wheel rotation speed detection unit, 3 is a calculation unit, 4 is a comparison/judgment unit, 5 is a storage unit, 6 is a signal generation unit, 7 is a reset unit, and 10 is an automatic gear shift unit. 11 is a torque converter, 12 is a main transmission, 13 is a sub-transmission, 14 is a drive gear, 15 is a front differential device, 16 is a front wheel drive vehicle, 17 is a propeller shaft for a rear wheel drive vehicle, 18 is a bevel gear ,1
9 is a center differential device, 20 is a rear wheel transmission device, 2
1 indicates a center differential lock device.

Generally, in a four-wheel drive vehicle with a center differential,
If the engine is mounted on the front side, the third
The driving force transmission mechanism is as shown in the figure. That is, the power from the engine is transferred to the torque converter 11 disposed within the automatic transmission 10, the main transmission 12,
The output is transmitted to the auxiliary transmission 13, and the output thereof is transmitted to the front wheel drive shaft 16 via the drive gear 14, the center differential device 19, and then the front differential device 15, thereby driving the front wheels. On the other hand, the propeller shaft 17 for rear wheel driving force is connected to a center differential device 19 via a bevel gear 18 .

In such a power transmission system, in the present invention,
A center differential lock device 21 is disposed in parallel with the center differential device 19, and when occurrence of slip is detected, the center differential lock device 21 is operated based on a control command signal.
This disables the front/rear wheel differential function.

Next, we will explain the concept of slip detection, which forms the basis of the present invention, in the fourth section, which shows temporal changes in various variables.
This will be explained based on the drawings and FIG.

First, Figure 4 is a time chart when no slip occurs, where θ is the accelerator opening, V _f and V _r are the rotational speeds of the front and rear wheels, Δθ is the rate of change of θ, ΔV _f , ΔV _r represents the rate of change of V _f and V _r , and ΔV _f , _r /Δθ represents the ratio of ΔV _f and ΔV _r to Δθ. Note that V _f and V _r are not necessarily the same value due to the operation of the center differential, but they change in the same way, so they are drawn together here as a diagram showing their trends.

As shown in Fig. 4, when slip does not occur even if the accelerator opening θ increases, the rotational speeds V _f and V _r of the front and rear wheels also increase accordingly.
It can be seen that the ratios of ΔV _f and _r /Δθ are constant values.

On the other hand, Fig. 5 shows a time chart of various variables similar to Fig. 4 when a slip occurs, but when a slip occurs, the wheels spin at high speed, so the rotation speed V _f and V _r rises rapidly, and along with this, its temporal changes, ΔV _f and ΔV _r , also rise rapidly. Therefore, ΔV _f , _r /
Since the ratio of Δθ also increases as shown in FIG. 5A, by monitoring this increasing state, it is possible to reliably detect the point at which a slip occurs. In addition,
ΔV _f and ΔV _r increase as the wheel rotational speeds V _f and V _r increase even if no slip occurs, so an increase in ΔV _f and ΔV _r does not necessarily mean a slip condition. do not. Therefore, ΔV _f ,
It is easy to detect the slip occurrence point not by the rise in ΔV _r but by the rise in ΔV _f , _r /Δθ.

Next, one embodiment of the control system in the control device of the present invention will be described with reference to FIG. 1. The front and rear wheel rotation speed detection sections 2 detect the respective rotation speeds of the front and rear wheels. The detection signals from each of the detection units 1 and 2 are input to the calculation unit 3, where the ratio of the rate of change in the front and rear wheel rotation speeds to the rate of change in the accelerator opening at that point in time (Fig. 4, ΔV _f , _r /Δθ in Figure 5)
is calculated, and its value is compared and input to the determination section 4.
On the other hand, the storage unit 5 stores a similar calculated value from an infinitesimal time ago, and inputs that value to the comparison/judgment unit 4 to compare the current calculated value with the calculated value from an infinitesimal time ago. . If the current calculated value is larger, it means that ΔV _f , _r /Δθ is increasing in FIG.
Generates a deflock signal from. Also, the reset section 7 resets the value in the storage section 5 to a new value at this time.

FIG. 2 shows the flow of processing in this control system, which will be explained in detail as follows.

Accelerator opening θ and front/rear wheel rotation speed V _f , V _r
Detect.

Rate of change Δθ and V _f of θ, rate of change ΔV _f of V _r ,
Calculate ΔV _r . This calculation can be done by using a differentiating circuit or by using θ, V _f ,
This can be done by counting each change in V _r .

Determine whether Δθ is 0 or not.

When Δθ is 0, that is, when the accelerator opening θ is not changing, the control signal for the center differential device is maintained unchanged. In other words, when Δθ is 0, this is because the state of slip occurrence (part C) or non-slip occurrence (part B) continues, as seen in changes B and C of Δθ in Fig. 5. be.

If Δθ is not 0, X _f = ΔV _f /Δθ, X _r =
Calculate the values of ΔV _r /Δθ, respectively. At this time, due to the inertia of the vehicle, the change in θ and V _f ,
Although a slight time lag occurs between changes in V _r , this can be dealt with in the design by using a time delay element commensurate with this.

Determine whether Δθ is positive or not.

Here, when Δθ is positive, the minute time Δt seconds ago value X _f0 and X _r0 stored in the storage unit and the current value
X _f and X _r are compared, and if either of the current values is increasing, it is determined that the slip condition shown in FIG. 5A is present, and a defrock signal is generated.

In the above case, when Δθ is negative and the defrock signal has been output until then,
As shown in FIG. 5D, since the accelerator opening θ is decreasing and the slip condition is eliminated, the defrock signal is canceled. Furthermore, if the differential lock signal is not being issued, it is impossible for a new slip condition to occur due to a decrease in the accelerator opening θ, so the current state is maintained (that is, the center differential is activated). .

In the above case where neither X _f > X _f0 nor _{X r >}
Since the slip states are E, E' and slip state F, the signal related to the center differential is maintained as it is.

Finally, the contents of the memory section are reset to new ones.

Repeat ~ above.

As is clear from the above explanation, according to the present invention, an abnormal condition such as a slip is detected promptly and the center differential is locked, thereby maintaining a stable and safe running condition that fully utilizes the driving force. can. Further, by providing a sensor for detecting the accelerator opening degree and the rotational speed of the front and rear wheels, and an electronic arithmetic and control unit, it can be realized with a simple configuration.

[Brief explanation of drawings]

FIG. 1 shows one of the control systems in the control device of the present invention.
A diagram showing the configuration of an embodiment, FIG. 2 is a diagram for explaining the flow of processing by the control device of the present invention, and FIG. 3 is a power transmission system of a four-wheel drive vehicle with a center differential to which the control device of the present invention is applied. 4 is a diagram showing a time chart of various variables when no slip occurs, and FIG. 5 is a diagram showing a time chart of various variables when a slip occurs. DESCRIPTION OF SYMBOLS 1...Accelerator opening detection part, 2...Front/rear wheel rotation speed detection part, 3...Calculation part, 4...Comparison/judgment part, 5...Storage part, 6...Signal generation part, 7...Reset part, 10...
Automatic transmission, 11... Torque converter, 12... Main transmission, 13... Sub-transmission, 14... Drive gear, 15
...Front differential device, 16...Front wheel drive force, 17...
Propeller shaft for rear wheel drive force, 18... bevel gear,
19... Center differential device, 20... Rear wheel transmission device,
21...Center differential lock device.

Claims (1)

[Claims] 1. A four-wheel drive control device equipped with a center differential that allows a difference in rotational speed between the front and rear wheels to absorb the difference in turning radius between the front and rear wheels that occurs during cornering. , detects the accelerator opening and the rotation speed of the front and rear wheels, compares the rate of change in the rotation speed of the front and rear wheels with the rate of change in the accelerator opening, and detects the change in the rotation speed of the front or rear wheels. 1. A four-wheel drive control device comprising a mechanism for locking a center differential and disabling an operating mechanism when the rate of change in the degree of change in the degree of accelerator opening becomes significantly larger than the rate of change in the degree of accelerator opening. 2. To compare the rate of change in the rotational speed of the front and rear wheels and the rate of change in the accelerator opening, calculate the ratio between the rate of change in the rotational speed and the rate of change in the accelerator opening, and then 4. The four-wheel drive control device according to claim 1, wherein the control is performed by comparing with a calculated value.